Make sure you have a Florida SW Fishing License (or you are exempt)
https://www1.wildlifelicense.com/fl/
And take a look at the regulations:
http://myfwc.com/fishingareas.html
And beware of the National Marine Sanctuary areas:
http://floridakeys.noaa.gov/regs/welcome.html
That should keep you out of trouble. Rumor has it the Fish and Wildlife guys may pay a little more attention to visitors on our water...so ensure you have everything in order. They all seem to be pretty decent folks, but Keys people are very sensitive about the resources.
And if you haven't done Keys boating before, there is some good info on not running aground here:
http://nps.gov/bisc/visit/groundings.htm
Be careful, Keys navigation is a bit more advanced than other areas. Overall its very safe around here, you just have to pay close attention to channels and such.
Can't help too much with the fishing tips, I perfer to pick my own fish out with a speargun